This invention relates to a pneumatic differential drag force detector which responds to a predetermined magnitude of force over a sustained duration by releasing a signal which in turn activates a specified activity. More particularly, this invention relates to a pneumatic differential drag force detector which is adaptable to the head of an unarmed decoy missile for detecting air pressure forces on re-entry of the missile into the earth's atmosphere and for responding to the force of a predetermined magnitude for a sustained duration by igniting a rocket motor or related activity.
Various methods have been disclosed in the prior art for detonating a firing assembly which would in turn discharge a munition explosive. Missiles and related airborne artillery equipment are frequently activated directly or indirectly by means of air pressure forces. Ram air pressure routed through a conduit system is known for arming a munition. Murphy, U.S. Pat. No. 3,841,220, and Rongus, U.S. Pat. No. 3,974,773. Pneumatic or fluid pressure has also been used to arm a firing system powered by a coiled-spring. Czajkowski et al. U.S. Pat. No. 3,981,329, Hermanson, U.S. Pat. No. 4,015,533, and Anderson et al. U.S. Pat. No. 3,962,974.
In the case of atomic warheads, the missile is often traveling at an altitude of 200,000-300,000 feet. The air pressure at this altitude on a sensor several inches in diameter, even at very high velocities, is only on the order of a few grams. As the missile descends, the air pressure increases. At a predetermined point the ignition of a rocket motor or related activity is desirable. Therefore, a very sensitive and durable drag-sensing body is required to detect small forces above a predetermined magnitude and initiate a response due to that detection. At the same time, the drag-sensing body must be capable of withstanding proximate nuclear blasts--defined as nuclear hardness. The sensor system must filter out short duration forces above the predetermined magnitude which will move the body. Only a force above the predetermined magnitude which remains for a predetermined length of time must activate the system.
The detonation on the firing assembly via signals from a sensor may initiate a number of activities other than discharging an explosive. For example, it may activate a relay which controls the ascension or descension of a craft. It may also ignite a rocket motor as noted above. In Chevrier et al. U.S. Pat. No. 3,992,999, a barometer is used to trigger a firing assembly which releases a parachute. It is obvious to those skilled in the art that may types of activities may be initiated by discharging a firing system.
It has been a particular problem, however, to develop a sensitive and durable sensing device which can remain inoperable for an indefinite length of time yet activated on a short time notice with assured reliability of performance. The prior art is complicated by a plurality of mechanical components which significantly inhibit their ability to remain inoperative for extended lengths of time. Achieving an accurate degree of sensitivity has also posed a particular problem in the field. As discussed above, the force from air pressure is generally on the order of only a few grams at the high altitudes traveled by atomic warhead missiles. While it is very important that the sensing means correctly monitors the environment, it is particularly important that the sensing device be inoperative to short duration forces such as proximate atomic blasts which may artificially release the trigger in conventional detonators.
An additional problem in the art has been the availability of an activation system responsive to sensing means which operates with a minimum amount of mechanical components. Again there is the need for an activation system capable of remaining inoperative for an indefinite lengths of time. The prior art is complicated by a plurality lock stems, shear pins, O-rings, etc.
There is a need, therefore, for an efficient, accurate, durable and reliable sensor and activation system responsive to environmental conditions for activation of a firing assembly thereby discharging a munition explosive, rocket motor, or related activities.
The problems enumerated in the foregoing are not intended to be exhaustive but rather are among many which tend to impair the effectiveness of the prior art at the high altitudes and speed concerned. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that the present art available to users of a sensing and detonating device has not been altogether satisfactory.